25C-NBOME is extremely potent and has been known to cause hospitalizations and even deaths at levels as low as 4mg. In two fatalities in Mankato, Minnesota in March 2014, the local distributor reportedly put "15-25" milligrams of 25C-NBOMe into each capsule that he sold, obviously assuming that users would further break the amounts into individual doses. It is unclear how much of the drug each of the decedents took.

Incident: Chloe Moses, 17, March 7, 2014 in Mankato, Minnesota

Chloe Moses took some or all of a capsule of material reportedly sold as "2C" by local Mankato, Minnesota news organizations, along with her friend TC Hafner (also 17 years old), and was taken to the hospital by her mother unresponsive and died at the hospital on March 10th. The toxicology report identified the substance as "25C1-NBOMe".

Louis Folson, 22, died March 5 in his Mankato apartment after taking the synthetic drug identified as 25C-NBOMe. Chloe Moses, 17, a Mankato West High School student, took the same drug and was taken to a hospital March 8 after her mother arrived home to find her having seizures. She was taken off life support March 10.

Inman is accused of obtaining a synthetic drug known as "2C" from Caputo and selling it to Louis Nathan Folson, 22. Folson died March 5 after taking the drug with another man at his Mankato apartment. A 15-year-old boy, who has not been identified by authorities, allegedly obtained the same drug from Caputo and sold it to Trace Colton Hafner, 17, of Blue Earth. Hafner and his girlfriend, 17-year-old Chloe Leah Moses of Mankato, took the drug at Moses' mother's house in Mankato on March 7. [...]Another man was with Folson and also took the drug, specifically identified in toxicology reports as 25C1-NBOMe.

Incident: Louis Folson, 22, March 5, 2014 in Mankato, Minnesota

Louis Folson took some or all of a capsule of what was reportedly sold as "2C" and reportedly became violently ill within 30 minutes of taking the substance. An ambulance was called and Mr Folson was found not breathing and declared dead at the hospital the same day. The toxicology report identified the substance as "25C1-NBOMe".

Inman is accused of obtaining a synthetic drug known as "2C" from Caputo and selling it to Louis Nathan Folson, 22. Folson died March 5 after taking the drug with another man at his Mankato apartment. A 15-year-old boy, who has not been identified by authorities, allegedly obtained the same drug from Caputo and sold it to Trace Colton Hafner, 17, of Blue Earth. Hafner and his girlfriend, 17-year-old Chloe Leah Moses of Mankato, took the drug at Moses' mother's house in Mankato on March 7. [...]Another man was with Folson and also took the drug, specifically identified in toxicology reports as 25C1-NBOMe.

Incident: Samnuel Herrera, 16, April 2013

In Apr 2013, 16-year-old Samnuel Herrera died in Fredericksburg, TX after insufflating a powder that has been tentatively identified as 25C-NBOMe. Lab tests are still under way. One other individual was hospitalized.

Samuel Herrera, 16, died Saturday after taking what police are calling a legal drug, 25c-NBOMe. [...] "We went into the house, and the officers found one of the kids unconscious, and the other kid was hallucinating severely," said Wetz. [...] Jarreau was rushed to a hospital in San Antonio where he is currently recovering, but Herrera was pronounced dead.

It is extremely difficult to determine an LD50 for a drug in humans. LD50s are only ever experimentally determined in animals, and extrapolations from one species to another for lethal dose are notoriously unreliable. With a new drug like 2C-C-NBOMe, there often isn't any animal data to extrapolate from.